1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of Related Art
A fixing device is an important component which constitutes an image forming apparatus and is a part necessary for fixing toner to a paper. Usually, only one fixing device is provided per one image forming apparatus. However, there is a case where two fixing devices are provided in one image forming apparatus. Reasons for providing two fixing devices in one image forming apparatus is for assuring sufficient fixation and for improving gloss (gloss level) of an image, for example.
As for the image forming apparatus in which two fixing devices are provided, there are conventional arts shown bellow, for example.
In JP 2005-316046, there is disclosed an image forming apparatus in which a cooling device is provided between the first fixing device and the second fixing device and thereby gloss change of an image is controlled to prevent degradation of image quality.
In JP 2007-148430, there is disclosed an image forming apparatus which obtains a good gloss image without greatly increasing power consumption by controlling the set temperature of the first fixing device, in a case where fixing is carried out by using both of the first fixing device and the second fixing device, so as to be lower than the set temperature of when fixing is carried out by only using the first fixing device.
However, the arts disclosed in JP 2005-316046 and JP 2007-148430 are arts for preventing degradation in image quality due to gloss of an image by controlling the heating temperature of the fixing devices.
A problem with providing a plurality of fixing devices is that the toner on the paper which passed the first fixing device is heated and softened and that roller marks, scratch marks and the like are formed at contacting positions by the toner which is in the softened state contacting with a conveyance roller, a conveyance path switching nail and the like.
In JP 2005-316046 and JP 2007-148430, there is no description or teaching regarding degradation of image quality due to the roller marks, scratch marks and the like.